LESSON VII 



Examination of Air and Dust Plate Culture Method Aspiration 

 through Broth Filtration through Sugar 



Examination of Air and Dust 



I. PLATE CULTURE METHOD. 



(1) Prepare three gelatine plates, and expose them to 

 the air at different spots and levels in the room for half an 

 hour, one, and two hours respectively. 



(2) Then cover them up with sterile lids, and place 

 them in the cool incubator. 



(3) Examine the plates and count the colonies from 

 day to day. 



The plates which have been kept nearest the floor, 

 or have been in a draught, will contain most 

 colonies. The number of colonies will also vary 

 with the time of exposure. 



Prepare subcultures in gelatine (streak cultures) of 

 the various colonies. 



' Various kinds of Staphylococci, Sarcinae, and Torulae 

 or Yeasts, or even Cladothrix, probably will be 

 found. 



